1. Field of the Invention
The present invention relates to a diagnostic ultrasound apparatus, and more particularly to a diagnostic ultrasound apparatus for carrying out diagnosis and measurement of movement of living body tissue based on two-dimensional ultrasound image data.
2. Description of the Prior Art
In general, two-dimensional ultrasound images are used to inspect and measure abnormal movements of living body tissue, for example, abnormal movement of a cardiac muscle caused by the stenosis or a coronary artery. Here, a coronary artery means an artery which sends blood to heart tissue. In the case where a stenosis occurs in such coronary artery, the portion or a cardiac muscle receiving blood from such coronary artery does not get supplied with a sufficient amount or blood. For this reason, the movement of such cardiac muscle portion becomes lowered, and this gives rise to abnormal movement. Now, when a method of observing such abnormal movement is carried out using two-dimensional ultrasound images, the two-dimensional ultrasound image corresponding to the contraction stage (systole) or the expansion stage (diastole) of the heart ventricle are first displayed on a monitor. Then, the cross-sectional area of the heart ventricle is measured based on the obtained two-dimensional ultrasound image, and a certain value calculated from the thus-measured cross-sectional area value is compared with a prescribed reference value which shows normal condition, whereby the abnormal movement of the cardiac muscle is observed and measured based on the difference between the calculated value and the reference value.
Furthermore, there exists an X-ray image forming process as a method of inspecting stenosis of coronary arteries (coronary angiography). In such coronary angiography method, a catheter is first inserted directly into an artery of an arm or thigh, and then an image forming agent is passed into the coronary artery through the catheter. Then, an X-ray picture of the coronary artery is taken. The thus-obtained X-ray image is used to observe the stenosis of the coronary artery.
However, the prior art process of carrying out diagnosis of abnormal movement of the heart by measuring the cross-sectional area of the heart ventricle based on ultrasound images is quite complex and therefore requires much time to carry out such measurements, thus making it impossible to achieve the long-desired goal of shortening measurement time. Furthermore, because measurements of abnormal movement are carried out based on the difference between a prescribed reference value and the cross-sectional area value of a heart ventricle during the systole or diastole thereof, it is very difficult to identify the portion where abnormal movement occurs in the living body tissue. In particular, in the case where the amount or abnormal movement of the living body tissue is small, the change in cross-sectional area is also small, and this results in a low accuracy of detection.
Furthermore, in the coronary angiography method, since a catheter must be directly inserted into the blood vessel and X-rays must be passed through the living body, the level of safety of such method can not be considered to be sufficiently high.